Transmission method for packet data and a network element

ABSTRACT

In packet data transmission method, a packet data connection is indicated with a connection identifier and the destination of the packet data connection is indicated with a destination identifier. A destination identifier is involved in the initialization of a transmission queue, at least one connection identifier is related to each transmission queue, and a set of proper connection identifiers is the union of the connection identifiers related to the initialized transmission queues. A data packet having a proper connection identifier is placed ( 504, 505 ) to the corresponding transmission queue. The method is characterized in that the initialization of a new transmission queue is triggered ( 506, 508 ) by a data packet not having a proper connection identifier and having a destination identifier and after a successful initialization of a new transmission queue the data packet that triggered the initialization is placed ( 509 ) to the new transmission queue. The method can be employed, for example, in a network element ( 800 ).

PRIORITY CLAIM

This is a national stage of PCT application No. PCT/FI01/00599, filed on25 June 2001. Priority is claimed on patent application Ser. No.20001509 filed in Finland on 26 June 2000.

FIELD OF THE INVENTION

The invention relates in general to packet data connections in cellularnetworks. In particular the invention relates to reserving resources forthe packet data connections.

BACKGROUND OF THE INVENTION

Traditionally cellular networks have been circuit switched networks,i.e. a certain part of the data transmission capacity both at the fixednetwork and in the radio access network is reserved for each call. Thiscapacity is reserved during the whole call, even if no speech or otherdata is transmitted.

The popularity of applications that can be run conveniently over packetswitched networks, applications such as electronic mail and browsing theWorld Wide Web, has caused need to enhance current cellular networks tosupport packet switched connections. For example, in Global System forMobile communication (GSM) packet switched connections are provided byGeneral Packet Radio Service (GPRS). Existing GSM networks can beupdated to carry packet data by adding proper network elements. WithGPRS it should be possible, for example, use the radio resources in theradio access network more economically than by transmitting packet datain a circuit switched connection, i.e. in a data call, as can be done inGSM.

Universal Mobile Communication System (UNITS) is one of the futurecellular networks that offer larger data transmission capacity thancurrent cellular networks. UMTS supports packet switched connections,and same GPRS equipment as in GSM networks may be used there. In fact,GSM radio access networks and UMTS radio access networks may beconnected to a common GPRS core network.

FIG. 1 presents a schematic diagram of an exemplary GSM radio accessnetwork and GPRS core network. A mobile station (MS) 101 communicateswith a base station (BTS) 102. One or more base stations are connectedto a base station controller (BSC) 103 that is responsible, for example,for allocation of radio resources and for handling handovers, where amobile station changes the base station it communicates with. The basestations and base station controllers form the GSM radio access network.In addition to these components, a GSM network comprises Mobile ServiceSwitching centers (MSC), Home Location Register (BLR) and VisitorLocation Register (VLR). ELR and VLR take part in, for example,subscriber and mobility management.

The GPRS core network comprises GPRS supporting nodes (GSN). Of thesenodes, the one which is on the edge towards a public data network, forexample the Internet, is called Gateway GPRS supporting node (GGSN). InFIG. 1, a GGSN 105 is presented. Data packets may run through many GSNs,which act as routers. A mobile station, which is the endpoint of thedata connection, is reachable through one base station controller andthe GSN connected to this base station controller is called Serving GPRSsupport node (SGSN). In FIG. 1, the mobile station 101 is reachable viathe BSC 103 and the GSN connected to this BSC is SGSN 104.

User data is transferred transparently between the MS and the externaldata networks with a method known as encapsulation and tunneling: datapackets are equipped with GPRS-specific protocol information andtransferred between the MS and GGSN. In order to access the GPRSservices, a MS first makes its presence known to the network byperforming a GPRS attach. This operation establishes a logical linkbetween the MS and the SGSN, and makes the MS available for, forexample, paging via SGSN and notification of incoming GPRS data.

The SGSN is at the same hierarchical level as the MSC, keeps track ofthe individual MSs' location and performs security functions and accesscontrol. The Gateway GSN provides interworking with externalpacket-switched networks, and is connected with SGSNs via an IP-basedGPRS backbone network.

FIG. 1 presents also exemplary protocol stacks that may be used in eachnetwork element for transmitting packet data. The GGSN 105 has protocolstack 115. The physical layer and the medium access layer are notspecified and they are represented with symbols L1 and L2 in FIG. 1. Theprotocol on the medium access layer protocol is Internet Protocol (IP),and on IP both User Datagram Protocol (UDP) and Transfer ControlProtocol (TCP) may be run. In GPRS core network, data is transmittedusing GPRS Tunneling Protocol (GTP). Data that is carried in the GTPpackets is either IP packets or X.25 packets, as specified by the upmostlayer in the protocol stack 115.

Towards the GGSN the protocol stack 114 of the SGSN is similar to thatof the GGSN. It lacks the upmost layer of the GGSN protocol stackbecause the data transmission protocol in GPRS core network is GTP. Abase station controller and the base station connected to it form a basestation system (BSS). The protocol stack 112 of a BSS is presented inFIG. 1, too. Towards a BSS the SGSN has a different protocol stack thantowards to GGSN. The common physical layer of the SGSN and BSS is L1bis,and Frame relay is used in the second protocol layer. The upmostprotocol layer between the SSGN and the BSS is Base Station System GPRSprotocol (BSSGP). Over this protocol the SGSN still has Logical LinkControl (LLC) and Subnetwork Dependent Convergence Protocol (SNDCP). LLCand SNDCP connections are between the SGSN and a mobile station. Theinterface between a BSS and a SGSN is called Gb interface.

The base station system, or more precisely a base station, communicateswith a mobile station using GSM RF as the physical layer. On thisprotocol there are Medium Access Control and Radio Link Controlprotocols. The base station system relays the data and signalinginformation between the RLC and BSSGP. The protocol stack 111 of amobile station comprises LLC and SNDCP protocols on top of RLC protocol.On these protocols there is a packet data protocol which is common withthe GGSN. The application is the upmost layer in the protocol stack.

The protocol stacks in FIG. 1 are those related to data transmission.Signaling, which relates, for example, to mobility management andresource reservation is carried out using GSM Mobility Management andSession Management (GMM/SM) protocol in the place of SNDCP. Otherwisethe signaling protocol stacks are similar to the data transmissionprotocol stacks presented in FIG. 1.

In third generation future cellular networks, the base station subsystemcomprises a controller, which in UMTS is called a radio networkcontroller (RNC) and base stations connected to the RNC. The basestations are here referred to as third generation base stations (3G-BTS)in order to distinct them from the base stations of a GSM radio accessnetwork for example. FIG. 2 presents as an example of a third generationcellular network an UMTS radio access network. The mobile station 201that is compatible with the UMTS network is different from a GSM mobilestation 101. It communicates with a 3G-BTS 202 that is connected to aRNC 203. The RNC may be connected to a GPRS core network. This is inFIG. 2 marked by presenting the RNC connected to a GPRS supporting node104.

FIG. 2 presents also the exemplary protocol stack 212 of the UMTS basestation system. The protocol stack 212 is related to packet data.Towards a GPRS supporting node, the lowest protocol layer is the same asthat in the protocol stack 112 of the GSM base station system, but theupper layers in these protocol stacks are different. In UMTS basestation system, Asynchronous Transfer Mode (ATM) is used in the mediumaccess layer and GPRS tunneling protocol is the upmost protocol.

Because the protocol stacks in the UMTS base station system and in aGPRS supporting node are different, there is need for an interworkingunit. In FIG. 2, the interworking unit (IWU) 206 is presented as aseparate device, but it may be a part of the RNC or the SGSN as well.Towards the UMTS radio access network the protocol stack 216 of theinterworking unit is similar to that of the UMTS base station system,and towards the GPRS core network it is similar to the protocol stackwhich in an SGSN faces a radio access network. The protocol stack 216has only three layers, and the upmost data transmission protocols areBSSGP and GTP. The interworking unit relays the BSSGP data packetsfurther as GTP data packets and vice versa.

Signalling related to, for example, radio resource reservation andmobility management, is carried out using a Radio Access NetworkApplication Part (RANAP). In signaling protocol stack, the RANAPreplaces the GRPS tunneling protocol in the protocol stack 212 of theUTMS base station system and in the protocol stack 216 of theinterworking unit.

FIG. 3 presents a schematic drawing of a network, where a GSM radioaccess network 300 and an UMTS radio access network 310 are connected toa GPRS core network 320. In FIG. 3, the GSM radio access network 300comprises two base stations 102 a and 102 b, and a base stationcontroller 103. The UMTS radio access network 310 comprises two 3G basestations 202 a and 202 b, and a radio access network controller 203. TheGSM radio access network 300 is connected to the GPRS core network 320by connecting the BSC 103 to a SGSN 104 of the GPRS core network 320.The UMTS radio access network 310 is connected to the GPRS core network320 by connecting the RNC 203 to the same SGSN 104. The GPRS corenetwork 320 is connected to a public data network 330 using a GGSN 105.

In the GPRS core network 320 between the SGSN and GGSN a data streamrelated to a certain connection is identified usually with a certainconnection identifier, for example with a flow label. Each GTP packetcarrying data related to, for example, a certain IP connection, has thesame identifier.

In the GPRS core network, there are subscriber-specific orconnection-specific queues for the data packets. For each subscriberthere may be many GTP sessions, each of which has a unique identifier,for example the GTP flow label. In the GSM radio access network, thedata packet queues are cell-specific, so that the management of thequeues is easy in the BSC. Depending on the number of service classes,there may be many packet queues in a specific cell. In a SGSN, the BSSGPlayer is responsible for re-organizing the subscriber-specific datapacket queues to cell-specific queues. This re-organizing requiresinformation on the subscriber identifier to which a certain GTP flowlabel relates and on the cell in which the subscriber is. Thecorrespondence between a GTP flow label or other connection identifierand a subscriber identity may be determined, for example, in the processof radio access network resource reservations when a Packet DataProtocol (PDP) context is being set up.

In UMTS radio access network, the RNC expects the packets arriving fromthe GPRS core network to be organized in subscriber-specific queues.Therefore between the Gb and Iu interterfaces, for example in the IWU,the cell-specific data packet queues have to be re-organized tosubscriber-specific queues. An example is presented in FIG. 4, whichshows the BSSGP layer 400 and GTP layer 410 of an IWU 206. These layersare involved in transmission of user data, signaling data is transmittedusing the BSSGP and the RANAP.

The cell-specific data packet queues 411–414 are shown in the BSSGPlayer 400. In FIG. 4, the BSSGP layer comprises a switching entity 440,which is responsible for organizing the data packets toconnection-specific queues 421–422. As an example, data packets 401–403are shown to be heading to a certain cell in the UMTS radio accessnetwork 310. The data packets belong to different packet dataconnections, and therefore they are placed to separate transmissionqueues 421, 423 and 424. In FIG. 4, the switch management entity 441comprises information about connections A, B, C and D. For theseconnections a PDP context has been established between a mobile stationwithin the UPTS radio access network 310 and a GGSN. The information maybe received, for example, from a subscriber database in a SGSN. In FIG.4, a subscriber database 450 is presented and arrow 431 shows how thenecessary information in the database is signaled to the switchmanagement entity.

The problem is that in certain situations a SGSN may transmit packetstowards a UMTS radio access network without checking if the receivermobile station has successfully carried out resource reservation in theUMTS radio access network and has established a PDP context. In ahandover from a GSM radio access network to an UMTS radio access networkit may happen that the SGSN receives information from the GSM radioaccess network that a handover has been completed, but the UMTS radioaccess network has not yet reserved resources for the GPRS data relatedto this mobile station. The SGSN may direct downlink data at once to theUMTS radio access network, but in the IWU, or correspondingfunctionality incorporated to the RNC or SGSN, for example, there is noinformation about the PDP context. The IWU, for example, does not have aproper transmission queue where to place the data packets with a certainGTP flow label. It has to discard the data packets. Other packetsheading to other mobile stations within the UMTS radio access networkmay suffer from additional delays due to the time consumed by theprocessing of the data packet without a proper PDP context. Further, ifsome data packets are deleted without informing the SGSN, it may sendthe packets again without realizing that the problem is actually thelack of reservations or an unestablished PDP context in the UMTS radioaccess network.

SUMMARY OF THE INVENTION

The object of the invention is to present a method for transmitting datapackets reliably. A further object is to present a method fortransmitting data packets when proper transmission resources have notbeen reserved for the data packets before-hands.

The object of the invention is achieved by triggering resourcereservation on the arrival of unswitchable packets that comprise aproper identifier for carrying out the resource reservation.

A method according to the invention is a method for transmitting datapackets, where

-   -   a packet data connection is indicated with a connection        identifier and the destination of the packet data connection is        indicated with a destination identifier,    -   data packets are sorted into initialized transmission queues        before transmission,    -   a destination identifier is involved in the initialization of a        transmission queue,    -   at least one connection identifier is related to each        transmission queue,    -   a set of proper connection identifiers is the union of the        connection identifiers related to the initialized transmission        queues and    -   a data packet having a proper connection identifier is placed to        the transmission queue determined by the connection identifier,        and it is characterized in that the initialization of a new        transmission queue is triggered by a data packet not having a        proper connection identifier and having a destination identifier        and    -   after a successful initialization of a new transmission queue        the data packet that triggered the initialization is placed to        the new transmission queue.

A network element according to the invention comprises

-   -   means for storing data packet to transmission queues,    -   means for indicating the connections related to each        transmission queue with connection identifiers,    -   means for detecting a connection identifier in a data packet,        and    -   means for placing a data packet to an initialized transmission        queue whose connection identifier is equal to the connection        identifier in the data packet, and it is characterized in that        it further comprises means for triggering the initialization of        a new transmission queue on the arrival of a data packet not        having a connection identifier equal to any of the connection        identifiers of the transmission queues and having a destination        identifier.

The appended dependent claims describe some preferred embodiments of theinvention.

In a method according to the invention data packets, which are beingtransmitted from one place to another, are sorted to transmission queuesat some point of the connection. To each transmission queue packetsrelated to a certain connection or to certain connections are placed.From the queues the packets may be transmitted further according to somespecified priority rules, for example.

A transmission queue is initialized before packets are placed to thequeue. This initialization typically involves some transmission resourcereservations. Information about the destination of a connection istherefore needed, when a transmission queue is initialized. Thedestination identifier may be, for example, a network address of thedestination or a name of the destination. A connection identifier can beassociated to a certain transmission queue in the initialization or at alater stage. The invention does not specify, for example, a protocolusing which the connection identifier is related to a transmissionqueue. The connection identifier may be, for example, a flow label of acertain packet data protocol. In a method according to the invention,transmission queues may be initialized dynamically. The establishment ofa packet data connection involves the initialization of a transmissionqueue related to the connection.

Data packets having a connection identifier, which is equal to one ofthe queue identifiers of the initialized transmission queues, are placedto the queue having the same identifier. If a data packet comprises noconnection identifier or if the connection identifier it comprises isnot equal to any of the connection identifiers of the transmissionqueues, then there is no transmission queue where to place the datapacket. In this case, it is checked if the data packet comprises adestination identifier, using which a new transmission queue can beinitialized. If it comprises a destination identifier, theinitialization of a new queue is triggered, i.e. resource reservationsmay be carried out. If there is not a destination identifier in the datapacket, then the packet may be discarded.

The advantage of a method according to the invention is that if there isa situation where a connection has not been properly set up and there isno transmission queue related to a certain connection identifier, datapackets having that connection identifier can be transmitted furtherwithout an extensive delay or without the sender re-sending it. If, forexample, a mobile station has performed a handover and data packetsrelated to a certain packet data connection are sent to the new locationbefore information about the packet data connection is signaled to theradio access network, the arrival of a data packet heading to the mobilestation triggers the signaling necessary for establishing the packetdata connection.

Future, if the initialization of the transmission queue is notsuccessful, then the sender of the data packet may be informed not tosend data packets related to this certain connection.

The incoming data packets may be, for example, sorted to queues based ona different label or they may be unsorted. The invention does notspecify in which order the incoming data packets are processed.

Other objects and features of the present invention will become apparentfrom the following detailed description considered in conjunction withthe accompanying drawings. It is to be understood, however, that thedrawings are intended solely for purposes of illustration and not as adefinition of the limits of the invention, for which reference should bemade to the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described more in detail with reference to thepreferred embodiments by the way of example and to the accompanyingdrawings where

FIG. 1 shows a schematic drawing of a second generation radio accessnetwork and core packet network,

FIG. 2 shows a schematic drawing of a third generation radio accessnetwork and core packet network,

FIG. 3 shows a schematic drawing of a second generation and a thirdgeneration radio access network connected to a core packet network,

FIG. 4 shows a schematic drawing of transmission of data packets on theedge of a GPRS core network and a UMTS radio access network,

FIG. 5 shows a flowchart of a method for transmitting data packetsaccording to a first preferred embodiment of the invention,

FIG. 6 shows a flowchart of a method for transmitting data packetsaccording to a second preferred embodiment of the invention,

FIG. 7 shows a schematic drawing of transmission of data packetsaccording to the invention on the edge or a GPRS core network and a UMTSradio access network, and

FIG. 8 shows a schematic drawing of a network element and anarrangement, where methods according to any preferred embodiment of theinvention have been implemented.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

FIG. 5 presents a schematic drawing of a method 500 according to a firstpreferred embodiment of the invention. In this method, data packets aresorted to transmission queues. The sorting is done based on a connectionidentifier. Each data packet related to a certain connection, forexample, carries a same queue identifier.

In step 501 a data packet is taken under inspection. The data packet maybe, for example, an incoming data packet. In step 502 it is checked ifthe data packet comprises a connection identifier. If it does, then instep 503 the connection identifiers related to the transmission queuescurrently in use are checked. In step 504 the connection identifier inthe data packet is compared to the connection identifiers related to thetransmission queues. If there is a transmission queue to which theconnection identifier is related, then in step 505 the data packet isplaced to that transmission queue. This is the case when a certainpacket data connection has been successfully established to thedestination before the arrival of a data packet belonging to the packetdata connection.

If the data packet comprises no connection identifier or the connectionidentifier is not a proper connection identifier (i.e. none of theconnection identifier related to the transmission queues is equal to theconnection identifier in the data packet), the data packet cannot beplaced to any of the existing transmission queues. In step 506 it ischecked. If the data packet comprises a destination identifier. If thereis no destination identifier, it is not possible to find out where thedata packet is heading, and therefore it is discarded in step 507.

If the data packet comprises a destination identifier, for example anetwork address or a name of the destination, then it is possible toestablish a packet data connection towards the destination. In step 508the initialization of a new transmission queue is triggered, and theinitialization of the transmission queue may involve, for example,reservation of transmission resources and setting up a packet dataconnection. In step 509, the data packet is placed to the newtransmission queue.

If the data packet that triggers the initialization of a newtransmission queue does not comprise a connection identifier, theinitialization process has to establish one.

After one data packet is processed, either placed to an existing or to anew transmission queue or discarded, in the method according to thefirst preferred embodiment of the invention the next data packet isprocessed similarly.

It is possible that the initialization of a transmission queue is notsuccessful. The initialization may also take some time and during thistime it is advisable to process other data packets. FIG. 6 present aflowchart of a method 600 according to a second preferred embodiment ofthe invention where these issues are taken into account.

The method according to the second preferred embodiment of the inventioncomprises two simultaneous loops. The upper part of FIG. 6 presents theloop where it is checked, if a data packet can be placed to an existingtransmission queue. It comprises of steps 501–505 which are similar tothe steps of the method 500 according to the first preferred embodimentof the invention. If the processed data packet comprises no connectionidentifier or the connection identifier is not equal to any of theconnection identifiers related to the existing transmission queues, thenthe data packet is placed to a buffer in step 601.

The lower part of FIG. 6 presents the second loop of the methodaccording to the second preferred embodiment of the invention. In step602, a data packet placed to the buffer is taken under inspection. Instep 506 it is checked, if there is a destination identifier in the datapacket. If there is none, then the data packet is discarded in step 507and the next data packet in the buffer is processed in step 602. If thedata packet in the buffer comprises a destination identifier, in step508 the initialization of a transmission queue is triggered. Thisinitialization may involve, for example, reservation of transmissionresources using a specific signaling protocol. After a response isattained, it is checked in step 604 if the transmission queueinitialization was successful. If it was not possible to carry out theinitialization procedure, then a data packet is discarded in step 604.In step 604 the sender of the data packet (or the nearest network nodefrom where the data packet came) is informed that packets to thisconnection or to this destination should not be sent here. If theinitialization of the new transmission queue was successful, in step 505the data packet is placed to the new transmission queue.

Data packets related to a packet data connection between a public packetdata network and a mobile station reachable through a third generationcellular system can be processed using the method according to thesecond preferred embodiment of the invention. This method may beimplemented in the interworking unit between the GPRS core network andan UMTS radio access network.

FIG. 7 shows how a BSSGP protocol layer 400 in an interworking unit maybe modified to support a method according to the invention. Themodifications may be done to the switch management entity 700, forexample by adding a triggering entity 710 that performs the steps of thesecond loop of a method according to the second preferred embodiment ofthe invention. The triggering entity 710 comprises a buffer 711, wherethose GTP data packets that no not comprise a connection identifier, forexample a GTP flow label, for which there is a transmission queue. Totrigger resource reservation requires signaling, this is presented inFIG. 7 with arrow 720. The signaling may be done, for example usingRANAP signaling.

A data packet 701 that does not have a GTP flow label corresponding to aconnection for which resources have been reserved is placed to buffer711 (step 601 in FIG. 6). If the data packet comprises a destinationidentifier, for example an International Mobile Subscriber Identifier(IMSI), a Temporary Mobile Subscriber Identifier (TMSI) or a TemporaryLogical Link Identifier (TLLI), this destination identifier may besignaled to the radio access network. The triggering entity 710 in theBSSGP switch management entity may, for example, sent a triggeringmessage to the RANAP layer. The triggering message indicates thedestination identifier, which is necessary in the resource reservation.

After receiving the triggering message, the RANAP layer of theinterworking unit starts to reserve resources in the radio accessnetwork. For example, a BEARER_REQUEST message of the RANAP protocol maybe sent to the Radio Network Controller. The RNC may answer using eithera BEARER_REQUEST_COMPLETE message (resources for the packet dataconnection have been reserved) or a BEARER_REQUEST_FAILURE message(resource reservation was unsuccessful). After receiving the response,the RANAP layer of the interworking unit may notify the BSSGP layer ofthe interworking unit that resources have been reserved (step 604 inFIG. 6). Because the resources have been reserved, a transmission queue(queue 725 in FIG. 7) has been initialized in the BBSGP layer 400 andthe data packet can be placed to the queue. From the; transmission queuethe packet is further transmitted to the radio access network and to theright mobile station.

After reserving resources for a packet data connection, the RANAP mayautomatically update the subscriber database in, for example, SGSN byadding information related to the packet data connection there. It isalso possible that the BSSGP layer sends information about the packetdata connection to the subscriber database. The management of packetdata connections in radio access network usually requires thatinformation about the packet data connections is available in asubscriber database.

It is possible that transmission resources cannot be reserved, forexample because the mobile station the destination identifier indicatesis not in the cell the subscriber database indicates or because all theradio resources are already in use. In this case the triggering entity710 may inform the SGSN that sent the data packet that the mobilestation, to which the packet data connection is related, is notreachable through the RNC the SGSN expected (step 605 in FIG. 6). It maysignal the information directly to the subscriber database using, forexample, proprietary signaling or RANAP signaling. Thereafter the SGSNcan, for example, start paging the mobile station to update theinformation in the subscriber database.

Certain data packets, such as GTP-U packets which carry user data, donot carry any information about the mobile station. On the other hand,GTP-C packets, which carry signaling data related to the management ofthe actual GTP connections, carry information about the destinationmobile station, too. Therefore it is possible to place only GTP-Cpackets or other signaling packets to the buffer 711. Other packets, forexample GTP-U packets with a flow label not corresponding to any of thetransmission queues, may be discarded directly.

The re-organization of cell-specific queues to connection-specificqueues as presented in FIG. 7 may be performed, for example, in the SGSNbefore sending the data packets to the UMTS radio access network, in aninterworking unit, or in the RNC in the UMTS radio access network.

FIG. 8 presents a network element 800 where a method according to theinvention is implemented. The incoming data packets are received in theblock 801. The connection identifier detection block 802 performs thetasks related to step 501 of the methods according to the invention. Itmay, for example, check if the data packet comprises a certain datafield of a protocol header. The queue selection block 803 is responsiblefor choosing the right transmission queue for the data packet. Thetransmission queues block 804 comprises information about the connectionidentifiers for which proper resource reservations have been carriedout. The adding to queue block 805 adds the data packet to the correctqueue, and the queue initialization triggering block 806 is responsible,for example, for signaling related to resource reservations. From thetransmission queue the data packets are transmitted further in thepacket transmission block 807. The blocks may be implemented using, forexample, microprocessors and suitable software.

The network element according to the invention may be, for example, aSGSN in a GPRS core network, a IWU between a GPRS core network and anUMTS radio access network or a RNC an UMTS radio access network.

The methods according to the invention are not restricted to those usedonly in cellular networks. It is possible to use methods according tothe invention, for example, in packet data networks where transmissionresources have to be reserved before transmitting data packets.

The network elements according to the invention are not restricted tonetwork elements of cellular networks.

Thus, while there have been shown and described and pointed outfundamental novel features of the present invention as applied to apreferred embodiment thereof, it will be understood that variousomissions and substitutions and changes in the form and details of thedevices described and illustrated, and in their operation, and of themethods described may be made by those skilled in the art withoutdeparting from the spirit of the present invention. For example, it isexpressly intended that all combinations of those elements and/or methodsteps which perform substantially the same function in substantially thesame way to achieve the same results are within the scope of theinvention. Substitutions of elements from one described embodiment toanother are also fully intended and contemplated. It is the intention,therefore, to be limited only as indicated by the scope of the claimsappended hereto.

1. A method for transmitting data packets, comprising the steps of:indicating a packet data connection with a connection identifier andindicating a destination of the packet data connection with adestination identifier; sorting data packets into initializedtransmission queues before transmission; involving the destinationidentifier in an initialization of a transmission queue; relating atleast one connection identifier to at least one transmission queue, aset of proper connection identifiers comprises a union of the connectionidentifiers related to initialized transmission queues; and placing adata packet having a proper connection identifier to the transmissionqueue determined by the connection identifier; wherein theinitialization of the new transmission queue is triggered by a datapacket not having a proper connection identifier and having adestination identifier, and after successful initialization of the newtransmission queue, the data packet that triggered the initialization isplaced in the new transmission queue and a sender of a data packet isnotified if the initialization of the new transmission queue is notsuccessful.
 2. The method of claim 1, wherein activation of the newtransmission queue is triggered by the data packet not having a queueidentifier.
 3. The method of claim 1, wherein activation of the newtransmission queue is triggered by a data packet having a queueidentifier that is not a proper queue identifier.
 4. The method of claim1, wherein the connection identifier comprises a certain data field in aprotocol packet header.
 5. The method of claim 4, wherein the connectionidentifier comprises a flow label of General Packet Radio ServiceTunneling Protocol header and the destination identifier comprises acertain cellular network subscriber identifier.
 6. The method of claim1, further comprising the step of: reserving transmission resources in aradio access network when the initialization of the new transmissionqueue is triggered.
 7. The method of claim 6, wherein transmissionresources are reserved using Radio Access Network Application Part inUniversal Mobile Communication System.
 8. A network element, comprising:means for storing data packet to transmission queues; means forindicating the connections related to each transmission queue withconnection identifiers; means for detecting a connection identifier in adata packet; and means for placing a data packet to an initializedtransmission queue whose connection identifier is equal to theconnection identifier in the data packet; and means for triggering theinitialization of a new transmission queue upon arrival of a data packetnot having a connection identifier equal to any connection identifiersof transmission queues and having a destination identifier, wherein asender of a data packet is notified if the initialization of the newtransmission queue is not successful.
 9. The network element of claim 8,wherein the network element comprises an element of a cellular network.10. The network element of claim 9, wherein the network elementcomprises an element of a Universal Mobile Telecommunication System. 11.The network element of claim 10, wherein the network element comprises aradio network controller.
 12. The network element of claim 9, whereinthe network element comprises an element of a General Packet RadioService core network.
 13. The network element of claim 12, wherein thenetwork element comprises a Serving GPRS Supporting Node.
 14. A networkelement, comprising: a buffer for storing data packet to transmissionqueues; a transmission queues block for indicating connections relatedto at least one transmission queue with connection identifiers; aconnection identifier detection block for detecting a connectionidentifier in a data packet; an adder for placing a data packet into aninitialized transmission queue having a connection identifier which isequal to the connection identifier in the data packet; and a queueinitialization triggering block for triggering the initialization of anew transmission queue upon arrival of a data packet not having aconnection identifier equal to any connection identifiers oftransmission queues and having a destination identifier; wherein asender of a data packet is notified if the initialization of the newtransmission queue is not successful.